Iodine is an essential component of the thyroid hormones which are necessary for normal growth, development, and metabolism during gestation, infancy, and throughout life. Iodine deficiency disorders (IDD) affect more than a billion people worldwide, and IDD during pregnancy and infancy are a major cause of intellectual impairment and brain damage. Iodine deficiency, through its effects on the developing brain, has condemned millions of people to a life of few prospects and continued underdevelopment. On a worldwide basis, iodine deficiency is the single most important preventable cause of brain damage. Thus, an accurate assessment of population iodine status is necessary to inform public health policies and clinical research on iodine nutrition. Urinary iodine concentration (UIC) directly reflects dietary iodine intake and is the most common indicator used worldwide to assess population iodine status. Currently used methods for urinary iodine measurement either require expensive instrumentation with qualified personnel (inductively coupled plasma-mass spectrometry, instrumental nuclear activation analysis) or oxidative sample digestion to remove potential interferences prior to analysis by a kinetic colorimetric method originally introduced by Sandell and Kolthoff. The Sandell?Kolthoff method requires hour(s) long sample digestion process involving very harsh chemicals and high temperature and are therefore limited to well-equipped laboratories. This requires shipping frozen urine sample to the central laboratories for analysis, which adds complexity, cost and may take several days to weeks to get test results. Thus, there is a critical need for an easy-to-use and cost-effective method for on-site testing of urinary iodine to support the mission of the global health communities. Lynntech is developing a simple innovative test kit for rapid and accurate measurement of urinary iodine concentration. In a Phase I SBIR study we have developed and demonstrated a rapid test kit consisting of dry test cartridges that only requires three simple steps for measurement of UIC using an inexpensive colorimeter. This test kit incorporates solutions to many challenging steps involved with the quantitation of urinary iodine, including detection of ppb levels of iodide in presence significantly higher concentration of potentially interfering anions and colored compounds, as well as removal of organic matrix. The goal of this Phase II of this SBIR project is to transition the technology into a practical test kit by developing a design for scaled up production of the test cartridges and testing the prototype test kit with large number of urine samples from school-aged children, reproductive-aged women, and pregnant women. The applicability of the test kit will be validated by comparing the results with those obtained by a standard spectrophotometric method. This technology can potentially make a significant impact on public health by making it possible to conveniently measure UIC much more frequently and providing accurate assessment of iodine deficiency at an individual basis.